Device for dosing of liquid

ABSTRACT

The device has a current supply (1) connected to a control unit (2) including operating keys (3). The operating keys (3) provide for the inputting of a selectable dose amount or dosage per time unit or dose period. A liquid reservoir (5) stores fluid to be expelled. A droplet generator (8) includes a plurality of jets (13) connected to piezo-electrical or thermo-electrical converters which generate heat. Each jet and associated converter is individually controlled by the control unit. The device provides exact dosing of extremely small amounts of liquid, for example in the medicinal field, specifically with respect to inhalators or infusion instruments.

BACKGROUND OF THE INVENTION

The present invention relates to the medical arts. It finds particularapplication in conjunction with a device for controlling the amount andrate of an administered dose of liquid. However, it is to be appreciatedthat the present invention will also find application in conjunctionwith other systems requiring delivery of selected amounts of a fluid.

It frequently happens in medical technology that additional doses ofsmall amounts of liquids need to be added, for example in an inhalatorto the flow of oxygen, over a certain period of time or in a specifieddosage to the infusion solution of an infusion apparatus. Similarproblems occur also in other areas of technology when relatively smallamounts of liquids need to be added or applied.

According to the invention, the solution is taking advantage of thetechnology which was developed for ink jet printers. An ink jet printhead has a multitude of jets (for example 12-300), which are connectedwith an ink reservoir. Each jet is assigned a thermo-electrical orpiezo-electrical converter. The converters are individually controlledby the printer and expel a volume of ink from the respective jet duringactuation.

It was possible to ascertain through tests that when a great manydroplets are expelled, the droplet mass, on average, remains almostconstant. Therefore, this principle is suitable also for dosing ofmedicaments.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, a device foradministering a dose of fluid is provided. A liquid reservoir stores thefluid and is in fluid communication with at least one jet which expelsdroplets of the fluid. A droplet generator which generates predetermineddroplets is connected to the at least one jet and causes the droplets tobe expelled through the at least one jet. A control unit selectivelycontrols the droplet generator to generate the predetermined dropletsand a current supply unit supplies the electrical power to the controlunit.

One advantage of the present invention is that a dose amount or dosagefrequency is selectable by an operator. The present invention providesexact dosing of even extremely small amounts of fluid to be delivered toinhalators, infusion instruments, or the like.

Still further advantages of the present invention will become apparentto those of ordinary skill in the art upon reading and understanding thefollowing detailed description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take form in various components and arrangements ofcomponents, and in various steps and arrangements of steps. The drawingsare only for purposes of illustrating a preferred embodiment and are notto be construed as limiting the invention.

FIG. 1 is a device for atomization of a liquid, specifically for aninhalator;

FIG. 2 shows one embodiment of a droplet generator in accordance withthe present invention;

FIG. 3 shows another embodiment of the droplet generator in accordancewith the present invention;

FIG. 4 shows one application of the present invention; and

FIG. 5 shows another application of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the invention is sketched in FIG. 1. Thisinvolves an instrument for atomization of liquids in the medical field.In case of illness of the respiratory tracts, it is necessary to finelydiffuse medicaments, i.e., to generate droplets of very small volume andlow velocity, in order to deliver them, though inhalation, to therespective locations where the effect is desired.

The device according to FIG. 1 has an energy supply 1 which includes,for example, a battery, an accumulator, solar cells or a current supply.In the event that an accumulator is the energy supply, a chargingdisplay may be included. The device has a control unit 2 which drives adroplet generator 8, facilitates turning the device on an off, andprovides for the input of an operating time or to select differentoperating modes, such as amount of dosage. Operation of the controller 2can, for example, be done in the form of control instruments such asbuttons 3 in connection with a display 4. Other operating possibilities,however, are also conceivable, for example, a remote control. A liquidreservoir 5 contains a liquid 6 that is to be atomized. The liquid 6 caninclude a single component liquid or mixtures. It is also possible todiffuse minute particles, so-called pigments, which are contained in aliquid matrix.

The liquid reservoir 5 is preferably designed as an exchangeable orreplaceable container, so that when the liquid volume is depleted, itcan be replenished in a simple manner. Alternatively, the liquidreservoir can be constructed to be refillable such as by a refill hole.In both instances, it is appropriate after replenishment of the liquidvolume to perform a rinsing process of the lines containing the liquidin order to guaranty safe operation of the device after the container isreplaced. This can be accomplished by a pump 7 which is located in thereservoir 5 or in the device. Preferably, a filling level monitor isused to control the level of the liquid. Thus, the filling level can bedisplayed or the depletion of the liquid in the reservoir can bedirectly observed.

With referenced to FIGS. 2 and 3, examples of droplet generator 8 areshown. One embodiment according to FIG. 2 has, in a housing 10, aplurality of narrow ducts 11 which all lead into a supply duct 12 forthe liquid 6 that is to be atomized. The duct 12 is connected withreservoir 5. Duct 11 carries the liquid to a liquid expelling jet 13.Preferably, the device includes a plurality of jets 13, each connectedto the liquid reservoir via a duct. An electrical heating element andconverter 14 is mounted to operate with each of the jets 13. Theconverter 14 is connected to lines 15. When a current impulse is appliedto the lines 15, heat is generated which causes a small amount of liquidto evaporate in an explosion-like fashion so that a liquid volume 16 isexpelled from the jet 13. After that, through capillary effect, the duct11 is again filled with liquid 6. The heating elements 14, theprotective layers and the conductor paths 15 are manufactured by thinfilm substrate technology, preferably on silicon as known by those ofordinary skill in the art.

In another embodiment shown in FIG. 3, the narrow ducts 11 lead into achamber 17 filled with the fluid 6. Above each jet 13 of the ducts 11 inchamber 17, a piezo-electrical bending converter 18 is included which iscontrolled via the lines 15. By applying voltage impulses to the lines15, the converter 18 bends back and forth which causes a liquid volume16 to be expelled from jet 13.

The converters 14 and 18 are preferably controlled via a continuous,uniform chain of impulses, controlled according to a selectedpredetermined time interval, programmed via a keyboard or input keys 3,or determined by a desired number of drops to be ejected. By selectingan impulse form and impulse frequency, the liquid volume can be variedwithin relative wide boundaries.

With ink jet print heads, depending upon the type, droplets aregenerated ranging in size between 30 and 300 ng (nanogram). The maximumimpulse frequency is approximately 10 kHz. With higher frequenciesand/or other impulse forms, however, significantly smaller droplet sizescan be generated, ranging between 1-10 ng, preferably about 4 ng. Thisdroplet size is ideally suited for inhalators. As a result of inhalingthe fluid vapor, additional fluid circulation results.

With reference to FIG. 4, another embodiment of the invention includesan apparatus which controls the precise dosage of small amounts ofliquid. It substantially contains the same components as the embodimentshown in FIG. 1. It comprises an energy supply part 21, a control unit22 with operating elements 23 and 24, a liquid reservoir 25 whichcontains the liquid that is to be metered out, and a droplet generator28. Here again, the liquid reservoir is, ideally, exchangeable orreplaceable in order to guaranty simple refilling of the device. To thatend, a pumping device 29 is included in order to purge any air occludedduring the replacement of liquid from the lines carrying the liquid outof the droplet generator. This ensures safe operation. In thisparticular application, the individual components are constructedseparately, inasmuch as there is no need for compact design.

The jets 13 and the operating mode of the converters, i.e., the appliedimpulse form is selected in such a manner that a highly constant dropletsize is created, such as for example 100 ng. Programming of the controlunit 22, via input 23 is performed to produce a desired dosage or dosageper time unit. From these values, the control unit ascertains therequired droplet size or the droplets per time unit. From this, thenumber and selection of converters 14 or 18 to be activated isdetermined, as well as the impulse frequency and, if necessary, thelength of the impulse sequence or the impulse number. The impulsefrequency may amount to in excess of 10 kHz. If the droplet generator 28for example, contains 300 jets 13, each with an associated converter 14or 18, the device can deliver a liquid amount ranging between 100nanograms and several dozen milligrams of liquid per second. As aresult, precise dosing of small amounts of liquid is achieved.

In FIG. 5, such an instrument 40 is employed for dosing of medicationsin infusions. In the connection line 41 and 44 between an infusionbottle 51 and a catheter 52 there is a drip unit 42. The drip unit 42prevents air from getting into the catheter 52 and thereby into theblood stream. It also permits visual display of the flow of the infusionliquid. The drip unit 42 comprises a hose 41, which is hermeticallyconnected with a transparent tube 43 having a larger cross-section thanthe hose 41. A second hose 44 is connected to the tube 43 andestablishes the connection between drip unit 42 and catheter 52. Theflow of liquid to the catheter 52 is determined, on the one hand, by thedifference in height between catheter 52 and drip unit 42, and, on theother hand, by the negative pressure which occurs in the drip unitvessel. The negative pressure in the drip unit 42 is, in turn, dependentupon the post-dripping infusion liquid, which, in turn, depends upon thedifferences in height and the available flow cross-sections. For thisreason, an adjustable throttle 45 is located in the supply line toregulate the flow.

The drip unit 42 is positioned in a suitable location for connection tothe dosing instrument 40. There must be assurance that the jet frontside 46 of the droplet generator 47 will not be moistened by theinfusion fluid 48 so that safe droplet ejection 49 can take place. Toprevent the dosing fluid from being sucked out of the droplet generator47 due to the commencing negative pressure in the drip unit 42, apressure compensation is provided via the connection 50 between the dripunit chamber and the dosing liquid reservoir.

Dosing of an additive is performed in a continuous manner by setting adesired droplet frequency for a given number of jets. Dosing of anadditive can be accomplished intermittently by setting a predeterminedtime period such that a selected number of droplets is expelled. Withthe device of this type, dosing extremely small amounts of liquid ispossible. Through aimed droplet ejection, it is also possible totopically accurately place an exact amount of liquid. However, for theabove described application, this is not required.

In an alternate application, the present invention can be used fordelivering lubricating agents in selected doses to a selected system,such as for lubrication of roller bearings. The accurate placement ofminute amounts of lubricating fluid by the present invention optimizesthe amount of spent lubricating agents. This requirement can also besatisfied by means of device 40.

The invention has been described with reference to the preferredembodiment. Obviously, modifications and alterations will occur toothers upon a reading and understanding of this specification. It isintended to include all such modifications and alterations insofar asthey come within the scope of the appended claims or the equivalentsthereof.

Having thus described the preferred embodiment, the invention is nowclaimed to be:
 1. A device for selectively administrating a dose offluid including a liquid medicament, comprising:a liquid reservoir forstoring the fluid; a plurality of jets for expelling droplets of thefluid into an inhalator; means for generating predetermined dropletsfrom the fluid stored in the liquid reservoir and expelling the dropletsfrom the plurality of jets in a selected fluid amount and a selectedfrequency, the means for generating the droplets including one of athermo-electrical and piezo-electrical converter, and including oneconverter connected to each of the plurality of jets for individuallycontrolling fluid expellsion from each of the plurality of jets; acontrol unit for selectively controlling the generating means togenerate the predetermined droplets; and a current supply unitelectrically connected to the control unit for supplying electricalpower.
 2. The device according to claim 1, wherein the liquid reservoiris attachable and detachable to the means for generating droplets. 3.The device according to claim 1 wherein the control unit generates afrequency and impulse form for controlling each of the converters togenerate droplets having a size between 1-10 nanograms.